as.matrix.xts fails when zero columns

[DarrenCook]

The xts:::as.matrix.xts function (

xts/R/matrix.R

Line 23 in 016b7cd

`as.matrix.xts` <-

) goes wrong when the xts object has zero-columns:

> xts:::as.matrix.xts(xts(c(),as.Date("2015-01-01")))
Error in dimnames(cd) <- list(as.character(index(x)), colnames(x)) : 
  'dimnames' applied to non-array

A first try at a patch looks like:

as.matrix.xts = function (x, ...) 
{
    if(length(x) == 0)cd <- matrix(,nrow=1,ncol=0)
    else cd <- coredata(x)
    dimnames(cd) <- list(as.character(index(x)), colnames(x))
    cd
}

I think it needs to be a bit more generic? But this was enough for me, and fixes a unit test that was complaining:

Error in dimnames(cd) <- list(as.character(index(x)), colnames(x)) : 
  'dimnames' applied to non-array
12: as.matrix.xts(x)
11: as.matrix(x)
10: as.vector(as.matrix(x), mode = mode)
9: as.vector.zoo(x, mode)
8: as.vector(x, mode)
7: as.vector(target)
6: all.equal.numeric(target, current, ...)
5: all.equal.default(target[[i]], current[[i]], check.attributes = check.attributes, 
       use.names = use.names, ...)
4: all.equal(target[[i]], current[[i]], check.attributes = check.attributes, 
       use.names = use.names, ...)
3: all.equal.list(target, current, tolerance = tolerance, ...)
2: all.equal(target, current, tolerance = tolerance, ...)
1: checkEquals(result, expected)

[joshuaulrich]

Thanks for the report. Here's a simplified example:

R> as.matrix(xts::.xts(,1))
Error in dimnames(cd) <- list(as.character(index(x)), colnames(x)) : 
  'dimnames' applied to non-array

Versus what you get with zoo:::as.matrix.zoo:

R> as.matrix(zoo::zoo(,1))

1
R> str(as.matrix(zoo::zoo(,1)))
 num[1, 0 ] 
 - attr(*, "dimnames")=List of 2
  ..$ : chr "1"
  ..$ : NULL

I think your proposed function provides similar results, but I'll likely follow the pattern in zoo:::as.matrix.zoo in case there's some edge case differences I'm not spotting.